Hybrid electric vehicles (HEV's), plug-in hybrid electric vehicles (PHEV's), and battery electric vehicles (BEV's) (hereinafter collectively referred to as “electric vehicles”) differ from conventional motor vehicles in that they employ one or more electric machines in addition to an internal combustion engine to drive the vehicle. Electric vehicles may also be equipped with a battery that stores electrical power for powering the electric machines. In some electric vehicles, an electric machine may also be employed as a generator that is powered by the internal combustion engine in order to generate electrical power to charge the battery.
Electric machines may incorporate synchronous motors having a stator and a rotor with permanent magnets. It may become necessary to determine a position of the rotor in order to meet electric motor control requirements of the electrical vehicle and to avoid inaccurate torque production.